Design of Filter Based on Loaded Dielectric Ridge Gap Waveguide Technology

This paper presents a U-band bandpass filter based on loaded dielectric ridge waveguide. By replacing the air layer with a dielectric substrate and integrating an air gap waveguide structure, a dual-layer U-band ridge gap waveguide is designed. To verify the feasibility of this waveguide technology applied in filter design, a half-wavelength resonator based on the loaded dielectric ridge gap waveguide technology is designed. Finally, the waveguide technology is combined with microstrip structures to simulate and design a U-band third-order half-wavelength coupled resonator bandpass filter and a parallel-coupled microstrip filter. To improve the filter's high selectivity, a U-band bandpass filter with a three-pole capacitor-type cross-coupled structure is designed. The center frequency of the designed filters is 55GHz, with an insertion loss of less than 3 dB in the passband, a return loss S11
$\boldsymbol{< -15\text{dB}}$
., and an out-of-band suppression of 30dB when the filter's rectangular coefficient reaches 3:1.